Safety latch for earthmoving scrapers



Nov. 12, 1963 w. E. LOTT SAFETY LATCH FOR EARTHMOVING SCRAPERS 4 Sheets-Sheet 1 Filed May 22, 1961 WA LT E i j E TT Nov. 12, 1963 w. E. LOTT SAFETY LATCH FOR EARTHMOVING SCRAPERS 4 Sheets-Sheet 2 Filed May 22, 1961 INVENTOR.

WALTER E. LO -T T Nov. 12, 1963 w. E. LOTT 3,110,118

SAFETY LATCH FOR EARTHMOVING SCRAPERS Filed May 22, 1961 4 Sheets-Sheet 3 FIG. 3

INVENTOR.

WA LTER E. LOTT Nov. 12, 1963 w. E. LOTT 3,110,113

SAFETY LATCH FOR EARTHMOVING SCRAPERS Filed May 22, 1961 4 Sheets-Sheet 4 INVENTOR! WALTER E. LOTT United States Pater Walter E. Lott, Washington, IlL, assignor to LeTourneau- Westinghouse @ompany, Peoria, lli., a corporation at Illinois Filed May 22, 1961, Ser. No. 120,111 13 Claims. (ill 37l2)) This invention relates to vehicles, especially to vehicles of the earthrnoving type wherein the reliability of braking systems is important.

Those who are skilled in the art of earthmoving are familiar with an equipment type which is known as a scraper, such a piece of equipment being one in whicu a carrying body is provided with a blade so positioned that the body can be lowered to bring the blade into contact with the ground while the body is in motion. The blade shaves a layer of earth loose and directs it rearward into the body or bowl. When the bowl is filled to some predetermined capacity, the bowl is raised to bring the blade out of contact with the ground. The body or bowl which is thus loaded is then taken with its load to some place where the earth thus removed can be utilized to raised the ground level. Earth is taken from a location known as the cut and is left in a location known as the fill. The time that it takes to move the load of earth from the cut to the fill is often a substantial part of the operating cycle, and thus it is in the contractors interest to keep such time to a minimum. Efiicient utilization of the equip ment dictates operation of the equipment at a high rate of speed between the cut and the fill, and safe operation at such high rates of speed requires reliable brakes.

In high speed operation of equipment of this type, brake failure can be offset in part at least by lowering the bowl until the blade contacts the ground, which action of course creates a tremendous resistance to forward motion and can be used in such an emergency to stop the forward motion of the scraper in case of brake failure. Other emergencies making such steps desirable occur from time to time, and will be apparent to those skilled in the art.

As is understood by those skilled in the art, under normal operating conditions, it is highly desirable that the bowl be kept out of contact with the ground during movement at high rates of speed between the cut and the fill. If the means for holding the scraper bowl out of contact with the ground should fail while the scraper is moving at high rates or" speed, and if the bowl should because of such failure drop to the ground against the Wishes of the operator, the resultant unexpected sudden stop can do a lot of damage to the equipment and can result in serious injury to the operator, who usually keeps moving forward for some distance even after the machine has stopped.

It is therefore desirable to provide means on such machines to secure the bowl or body against accidental dropping into contact with the ground. However, the equipment should be so designed that the means to prevent accidental dropping of the scraper howl will not interfere with dropping of the scraper bowl when the operator wishes to drop the bowl for emergency stopping of the scraper. Moreover, it is very desirable that the operator not have to concern himself at all with the auxiliary means to prevent accidental dropping of the bowl; instead, the equipment should be so designed as to prevent accidental lowering of the bowl due to equipment failure, but should allow the operator to drop the bowl when he wishes to do so in case of brake failure without performing any additional act or maneuver other than what he would normal- 1y do simply to lower the bowl for emergency braking purposes.

It is accordingly an object of this invention to provide a vehiclewherein an element can be lowered into the supporting surface for the vehicle, the vehicle being designd to permit raising and lowering of the element into contact with the supporting surface at the will of the operator and having provision to prevent accidental lowering of the element into contact with the supporting surface, with the further provision that the operator can deliberately lower the element into engagement with the supporting surface without making a conscious effort to overcome the provision which prevents accidental lowering of the element. This and other objects are accomplished in a vehicle having additional means for holding the element out of contact with the supporting surface in case of failure of that portion of the equipment which normally holds the element out of contact; the element may be lowered into contact with the supporting surface for emergency stopping without any thought or conscious maneuver on the part of the operator to rendering the additional holding means ineffective.

in the drawings:

FIG. 1 is a side elevation view of a vehicle embodying the invention, the vehicle here shown being a loading and carrying scraper.

FIG. 2 is a schematic view showing the various elements in their relationship to each other, the diagram shown in PEG. 2 being a representation of a preferred embodiment of the invention.

FIG. 3 shows a detail of the system of FIG. 2 but in a different operating position.

FIG. 4 is another view of the same detail shown in FIG. 3 but illustrating still another operating position; and

PEG. 5 is a schematic view comparable to FIG. 2 but showing another embodiment of the invention.

Referring n w to the drawings in detail, the vehicle seen in FIG. 1 will be recognized by those skilled in the art as a loading and carrying type of scraper in which a tractor indicated generally at 2 is connected to a trailing scraper unit indicated generally at 4. The tractor is provided with wheels, one of which is shown at 6 and the trailing unit is provided with wheels one of which is shown at 8. The wheels 6 and 8 will be equipped with any one of a number of suitable conventional brakes; one such brake which has been extensively used on equipment of this type is disclosed and claimed in Patent 2,453,237 issued to R. G. LeTourneau on November 9, 1948. The details of the wheel braking system form no part of this invention and are therefore not shown here.

The trailing scraper unit 4 includes the wheels 8 referred to above, a bowl it? mounted at its rear end on the wheels 8, a yoke 12 pivotally connected on each side to the bowl by any suitable means having a pivot axis shown at 1 and a blade 16 which constitutes an element to be lowered into contact with the supporting surface here shown at 18.

An opera-tors station is indicated generally at 2d and comprises an operators seat 22 and a control panel 24-. Means controllable by the operator are provided for raising and lowering the element 16 and for holding element to out of contact with the supporting surface or ground 18 while the vehicle is in transit between the cut and the fill or is otherwise in motion under circumstances that require the blade or element 16 to be held out of contact with surface 18. In scrapers to which the invention here disclosed and claimed has been and is being applied, the means for raising and lowering the element 16 and for holding it out of ground contact include a cable system. There are many different types of such cable systems and no specific cable system is shown here in detail. It will suffice to indicate that the cable system includes a cable drum, the drum being shown in FIG. 1 at 26. Additional means for holding element 16 out of ground contact in THE EMBonrMENr or Pros. 24

Although FIG. 1 suffices to show the several elements of the invention in their relationship to each other, the scale of FIG. 1 is rather small for a detailed discussion of the entire invention. Accordingly, reference will now be made to FlGS. 2-4 inclusive for a more detailed discussion of the invention. As shown in FIG. 2, cable drum 26 is connected to be driven byan electric motor 34 through a power train indicated generally at 36. In the preferred embodiment shown, the power train 36 is of the planetary type having a sun member, a ring memher, and a planet member. More specifically, in the embodiment here shown, the sun member is a sun gear 38, the ring member here shown is an internal ring gear 4ti,and the planet member comprises the usual planet carrier and one or more planetary gears; as here shown, the cable drum 26 serves as the planet carrier for a plurality of planetary gears 42, here shown as being two in number. As is conventional in planetary gear trains, the planetary gears 42 mesh with sun gear 38 and with ring gear 40. A cable 44 is shown as part of the cable system which is referred to above as forming part of the means controllable by an operator for raising and lowering the element 16. It will be understood by those skilled in the art that the cable 44 here shown is intended merely as being a schematic showing of any suitable cable system connected in any of a number of ways to the scraper bowl to raise and lower the same. Toward that end, cable 44 is here shown as wrapped around cable drum 26, and as being dead-ended by means of a loop 46 engaging a pin 48 which may be secured to or may be an integral part of the scraper bowl 14 (FIG. 1).

Sun gear 38 is secured to the end of a shaft Sti the other end of shaft 54} carries a brake drum 52. A brake shoe 54 ispositioned to engage the braking surface of brake drum 52 and is mounted on a piston rod 56 of a piston 58 which is reciprocable in acylinder 6% A spring 62 in one end of the cylinder 60 normally biases the brake shoe 54 into engagement with brake drum 52, whereby sun gear 38 forms the reaction member of the planetary power train when brake 54 is engaged under the influence of spring 62.

From the foregoing, it will be evident that the fluid pressure operated device consisting of piston cylinder 60, and spring 62 combines with brake 54 and brake drum 52 to form additional means to lower the'element 16 into engagement with the supporting surface 13, as will be described in greater detail further on in connection with the over-all description of the operation of the invention.

Electric motor 34 receives power from a three-phase alternator indicated schematically at 64. Alternator 64 is preferably part of an electrical system such as the one shown in Patent 2,844,783, issued July 22, 1958, to James I.' Chandler and Charles C. Roe and assigned to the same assignee as this invention. by those skilled in the art, alternator 64 is connected to be driven by any suitable prime mover, and preferably by the engine 66 mounted in the tractor 2 shown in FIG. 1. The three-phase power line 68 provided for the output of alternator 64 is connected with electric motor 34 through either one of a set of contacts indicated generally at 70 and 72. The contacts 7:? are part of a contactor indicated generally by the outline '71, while the contacts 72 are part of a contactor indicated generally by the outline 73. Contactor 71 is here shown schematically As will be understood as comprising an armature 71in connected to actuate the contacts 7% and a coil 716 which is electrically positioned 1 to attract armature 71a when the coil is energized and thus move the contacts 7% into their closed-circuit position. Any suitable spring, not shown, can be connected to open the contacts 76 upon de-energization of the coil. Contactor '73 is similarly provided with an armature 73a and a coil 73c.

Connection is made at the will of the operator who has mounted before him on the control panel a pair of small snap switches 74 and 76 to lower and raise respectively the scraper bowl and thus the element 16. Switches '74 and 7-6 are preferably of a type disclosed in Patent 2,629,791, issued February 24, 1953, to R. G. Le Tourneau; switches of this type can be arranged or connected so as to be normally open or normally closed; in the embodiment here shown, the switches 74 and 76 are arranged to be normally open. Although the switches 74 and 7 6 can be mounted on the control panel for completely independent operation, it will be understood by those skilled in the art that such an arrangement is undesirable because it permits simultaneous operation of the two switches and correspondingly simultaneous closure of the two sets of contacts 7% and 72 which would result in a dead short across the line of the alternator 64. To prevent such simultaneous operation of the switches, switches 74 and 76 may be, and desirably are, mounted for operation by a single operating lever as shown in FIG. 2 of Patent 2,950,633, issued August 30, 1960 to I. W. Goodrich. For the purposes of describing this invention, the illustration here set forth in FIG. 2 is adequate.

Reference was made above to the over-all electrical system disclosed and claimed in Chandler et al. Patent 2,844,783. The system shown in the Chandler et al. patent includes a storage battery 23 which is here shown (FIG. 2) as storage battery 78. One terminal of battery 73 is grounded as indicated at 8%. The other terminal is connected to a conduit 82 which is connected with another switch 84 by a conduit 36 and with a switch by a conduit i i). Switch 84 is of the same general type as switches 74 and 76, but is internally connected to be normally closed. Another conduit 92 connects switch with conduits M and 96. Conduit 94 is connected with switch 38, and conduit 96 is connected with one end of a coil 9% of a solenoid which is connected to operate a valve 1%.

Switch 88 referred to above may be any one of a number of simple electric switches. In the actual embodiment of the invention, switch 83 is a small snap switch like the switch '74, although of course that is not a requirement. Switch 88 is normally open as shown, and is associated by any suitable linkage with the contactor which carries the contacts 7% to connect motor 34 for lowering of element 16. It will be understoodthat the nechanical connection here shown at 132 is purely schematic and is merely intended to indicate that closure of the contacts 78 also closes switch 88 without any additional or conscious effort on the part of the operator.

Reference was made above to a solenoid which is connected to operate valve 1%. Coil 93 of this solenoid actuates an armature 104 against the bias of a spring 1&6 to move the valve 189 in one direction. Valve 1% is returned to the position shown in the drawing by spring when coil 9% is tie-energized.

As was pointed out above, one end of coil 5 8 is connected to conduit 96; the other end of coil 98 is grounded as shown at 1% through a conduit 11% and a normally closed snap switch 112, switch ii2'being, again, of the type referred to above as being disclosed in LeTourneau Patent 2,629,791.

Reference was made above to' the additional means for holding element 16 out of contact with the supporting surface or ground 18. The details of the additional means are better shown in FZG. 2, wherein it is evident that stop member is a rocker pivoted at 114 and is connected at 116 for movement about pivot 114 by the fluid pressure operated means 32 through the means of a suitable connecting or operating rod 113. The fluid pressure operated means or device 32 may be any suitable expansible chamber device. The specific device here shown comprises a case H9 in which there is mounted a diaphragm 120 which is movable to operate the rod 118. Diaphragm 12b is arranged to be subiect on its upper face as here shown to fluid under pressure; a spring 122 is disposed between the lower face of diaphragm 120 and the lower end of case 119.

Rod 118 carries an arm 12-: securely fixed thereon; arm 124 is positioned to engage the operating button of snap switch 112 at one extreme of travel of rod 118, this being the position illustrated in FIG. 3. Inasmuch as stop-engaging member 30 is securely mounted on and carried by bowl l0, and since bowl l pivotally engages yoke 12 at 14, the movement of stop-engaging member 3% relative to stop 28 is necessarily through the arc of a circle having its center at 14. Accordingly, if the movement of stop engaging member 30 is through a substantial arc, member 39 is desirably curved to conform to the are referred to. Otherwise, if stop-engaging member 39 has a configuration such that the face which engages stop member 28 in the operating position shown in FIG. 2 is a plane surface, it will be understood by those skilled in the art that an appreciable movement of member 3% would cam the stop member 23 about its pivot 114 sufficiently to cause the arm 124- to engage snap switch 112 at a time when such engagement might be undesirable. What the configuration of stop-engaging member 30 should be will depend to a large extent on the factors involved in each particular piece of equipment. The designer will be able to determine for the particular item being designed whether stop-engaging member 30 can have a plane surface or Whether the surface in engagement with stop member 28 should be curved to form an are having pivot 14 as its center.

Reference was made above to the fact that, in a preferred embodiment of the carrying scraper shown, fluid pressure operated brakes are associated with wheels 6 and 8, these brakes being of a type shown in Patent 2,453,237, referred to above. The fluid used is preferably air which is compressed by any suitable compressor connected to be driven by engine 66 and connected to supply air under pressure to a storage tank 126. In one embodiment of the invention, storage tank 12s is mounted on tractor 2 and is connected by an air line 123 with an auxiliary tank 130 which is preferably mounted on the trailing unit 4. A check valve 132 is desirably disposed in the line 128 close to tank 13% to insure that a break in the line between the tractor and the trailer will not cause tank 139 to lose pressure. Another high pressure air line 134 connects tank 139 with valve 1% by way of an air line 136. Valve Lilli is provided with a passage 138 and is connected with fluid pressure operated device 32 by means of air line 140. A vent to atmosphere 142 is provided on valve 190. In the operating position shown, line 14 0 is vented to atmosphere by way of passage 138 and vent 142.

Reference was made above to the additional means for lowering the element 16 into engagement with the supporting surface 18, this additional means being made up of the piston 58, cylinder ea, spring 62, brake shoe 54, and brake drum 52. In equipment of the type made by the assignee of this invention, this additional means is known as the quick-drop. The quickrop is controlled by the operator by a quick-drop handle 144 on a valve 146 having a fluid passage 148 and a vent passage 15 3. Two air lines are connected with valve 146, line 152. connecting valve 146 with cylinder 60 and line 154 connecting valve 146 with tank 130 by way of line 134.

Inasmuch as the quick-drop control is operated from the operators station 20, valve 145 is located on the tractor. This of course means that the air line 15 extends forward from air tank on the trailing unit 4 to the tractor 2. in some variations of the invention here shown, it might be desirable to eliminate the second long line forward from the trailer to the tractor. Such a variation is here indicated schematically by a cross-over air line 156 having in its valve 1558; another valve 16% is shown in line 154 and indicates schematically that this portion of line 154 may be closed off. In actual practice, valves 158 and 160 are of course not used. Instead, the length L of air line 154 is simply eliminated, in which case, valve 146 receives air under pressure directly from tank 126 instead of from tank 130. The functional equivalent of eliminating length L is here illustrated by the valved cross-over line 156 and the valve 169. Attention is invited at this point to switch 84 and operating handle 144 of valve 146. An arm 152 secured to handle 144 is positioned to engage the operating button of switch 84 by a spring 164 which normally holds operating handle 144 in the position shown, in which position the normally closed switch 54 is held open.

THE EMBGDIMENT OF FIG. 5

Reference will now be made to FIG. 5 for a description of the embodiment there shown. In general, this description will be limited to the features which distinguish the embodiment of FIG. 5 from the embodiment shown in the corresponding FIG. 2.

In the embodiment illustrated in FIG. 5, two solenoid operated valves 6% and oil are shown. Insofar as "al-ves 6% and 601 are used to control air flow to device 532 by operation of the quick-drop control handle 644, valves see and 6d]. are cormected in series by an air line 653. Valve dill-is provided with an air vent 655 and a assage 657. Line 653 connects with air line 659 by way of passage 657 when valve dill is in the operating position illustrated. Line 65h connects with line 652.

It may be noted that air line 646, which connects valve see with the fluid pressure operated device 532, is provided with a quick-release valve 641. Valve 641 may be one of a type shown in FIG. 2 of Patent 2,040,580 issued May 12, 1936, to Stephen Vorech.

Inasmuch as valve 6% and its control (PEG. 5) correspond closely to valve 10% and its control (FIG. 2),

the control circuit for valve 6130 need not be detailed here.

Valve 601 in FIG. 5 is operated by a solenoid having a coil 661 and an armature 663. Movement of valve dill to another operating position upon de-energization of coil 661 may be accomplished by a suitably connected spring, not shown here.

One end of coil 651 is connected with conduit 610 by means of a conduit 611; the other end of the coil is connected with conduit 5% by a conduit e13.

Operation In the operation of a scraper like that shown in FIG. 1, the brakes are relied on for normal deceleration or stopping of the vehicle. If the machine should suffer a brake failure, the operator can resort to quick-drop of the bowl for sudden stopping of the vehicle where such a sudden stop is required under emergency conditions, as where the vehicle must be stopped promptly to keep it from going over the side of a mountain road.

In normal operation of a scraper equipped with a cable system to raise and lower the scraper bowl, while the scraper is in transit, the bowl is carried by the cable of the cable system. (Iable is subject to wear, and sometimes a cable will break while the scraper is moving on the haul road at a fairly high rate of speed. In case of such cable failure, when the scraper is equipped with the invention here disclosed, the bowl does not drop unexpectedly all the way to the ground, but the hook or stop-engaging member 3% catches on the latch or stop member 28 before the bowl drops low enough to permit contact between the blade to and the ground, haul road, or other supporting surface THE EMBODZMENT OF FEGS. 2-4

Reference will be Jade again to FIGS. 2-4 for a description in greater detail of the operation of the embodiment there shown. When the operator desires to lower the scraper bowl by the means in which this is normally done, namely by the raising and lowering means which operates the cable drum 25, he actuates the switch 74 to complete a circuit for coil 71c of contactor 71. Energization of coil 72c closes the contacts 7% and corn pletes a circuit for motor 3 such as to unwind cable from cable drum 26.

Manifestly, such a maneuver by the operator would not succeed in lowering the bowl very far because stopengaging member 3i) would not get past the stop member 23, unless meanwhile something is done to render the additional holding means 23, ineilective.

When the operator closes a circuit for coil 71c and moves the contacts 79 into the closed circuit position, such movement closes switch Consequently, a circuit is completed from battery 78 through coil 3 by way of conduit 9% switch 8%, conduit 9 conduit )6, coil 98, conduit 11%, normally closed switch 112, and back to the battery through the grounded connections 1% and 89.

With coil 98 energized, valve ltltl is shifted to communicate air lines 336 and 14-53 by way of valve passage 13%. Air under pressure is thereupon free to move directly from air tank 134 to the device 32 by way of air lines 134, 236, and 14%. Air under pressure acts against diaphragm 1Z9, compressing the spring 122, moving the rod 113 downward, and pivoting the connected rocker arm clockwise about its pivot 114, Since the upper portion of the rocker arm is the stop member 28, the stop member is withdrawn or retracted into a position such that stop-engaging member 39 is unable to contact the latch or stop member 28, and bowl 1% is permitted to move downward, allowing blade 16 to bite or dig into the ground for the normal scraper loading operation.

At this point, it n ay be indicated that the scraper is normally in the bowl-down position during loading (and when parked for long eriods). As soon as the operator has lowered the bowl to the ground, he releases the operating button of switch 74 and thus opens switch This action interrupts the circuit for coil 93, re turning valve 16% to the operating position shown under the influence of spring 1%. In this position the pressure chamber above diaphragm 12% of device 32 is vented to atmosphere, and spring 32?. is permitted to expand. With stop-engaging member 3i": well below any position which could interfere with counterclockwise pivoting of member 28, the parts assume the position shown in FIG. 3, in which arm 124 engages the operating button of normally closed switch 31.12. Switch 112 thereupon opens and remains open as long as the parts occupy the position shown in H6. 3, assuring that coil 98 remains deenergized regardless of what now happens to switch 88. Thus, repeated operation of the means to render the latch ineffective is prevented during the normal up and down movements of the bowl while loading.

To resume operations, the operator starts engine 66 in order to drive alternator The operator can then close switch 76 and thus close a circuit for motor 34 to rotate the motor in a direction to wind cable onto the drum 26, raising the bowl 1 3 off the surface It will be noted that there isno provision for energizing coil 98 upon the operation of switch 76 because, first of all, contactor 73 is in no way connected for operation of switch 88. Moreover, under the assumed conditions (starting with the bowl resting on the ground), switch 112 is open and thus there is no possibility of completing a circuit at this time for coil 98. However, it is not necessary that the stop member 28 be positively pivoted out of the way of'stop-eugaging member 39' when the bowl is raised, because the member 3% is capable of camming the stop member 28 out of the way during such upward movement, as is best seen in FIG. 4. The operator raises the bowl until the upper end of stop-engaging member dll is again above the stop member 23, whereupon spring .122 clicks the stop member 2f: back into normal operating position, shown in FIG. 2.

For the raising and lowering of bowl 16* and blade 16 by means of the cable 44 as described immediately above, the sun member of the planetary power train serves as the reaction member because it is held against rotation by brake 54 acting on brake drum 52. Ring gear 41} is of course the input member and planet carrier (cable drum) 25 is the output member. Assume now that the operator wishes to accomplish quick-drop of the bowl for any reason. To this end, he strikes handle 144 a forward blow (leftward as seen in FIG. 2). During the first, very small, increment of movement of handle 144, arm 162 is lifted against the bias of spring 164- oif the op rating button of switch 84. motion immediately closes a circuit for coil 8 as follows: battery 73, conduit 82, conduit 86, switch 84, conduits $2 and 5 5, coil 93, conduit 11% switch @112, and ba 1; to the battery through the ground connections lda'iand 8! Thereupon, an air circuit is completed as follows: air tank 13 3, lines E34 and 136, passage 1'38 of valve 160, and line 14% to the pressure chamber of device 32. Device 32 thereupon pivots the stop member 23 clockwise as described above.

Meanwhile, as handle 144 is pushed further forward, or leftward as seen in FIG. 2, a passage 11 13 in valve 146 connects the air lines 154 and 152, allowing air under pressure to move from tank through lines 134 and 154, passage 148, and line 152, to the cylinder 60. Piston 53 thereupon compresses spring 62 and disengages brake shoe 54 from drum 52. V

What was up until now the reaction member of the power train is suddenly free to rotate under the influence of the load carried by cable 44. The result of course is a rapid lowering of the bowl 1% under the unimpeded influence of gravity, with stop member 23 safely out of the way.

Having recovered from the emergency or other conditions which prompted use of the quick-drop by the operator, the operator allows spring 164 to return handle 144 and arm 162 as well as valve 146 to the position shown in FIG. .2. Thereupon, vent passage 15h" connects line 152 to the atmosphere and allows spring 62 to reapply the brake, whereupon sun gear 38 is again the reaction member of the planetary train. Switch 84 is again actuated by arm 162 to interrupt the aforesaid circuit for coil 93, whereupon valve 16th returns to the operating position shown in FIG. 2 in which line 14% is vented to atmosphere. It will be noted by those skilled in the art that, if the quick-drop operation described above has allowed bowl dll to drop all the way to a position at rest on surface 13, a subsequent return of handle 144 to the position shown in 2 would de-energize coil 98 and allow the parts to take the position shown in FIG. 3, described above, in which switch 112 would interrupt the ground circuit for coil 98.

THE EMBODIMENT 05 FIG. 5

The operation of this embodiment is similar to the one just described as far as lowering the bowl by motor 534 under the control of switch 574 is concerned. Accordingly, this phase of the operation need not be repeated, except to point out that the quick-release valve 641 serves to vent the device 532 to atmosphere upon de-energization of coil 59%. This is desirable because the venting of device 532 to atmosphere by way of vent 655) in valve 64:; cannot always be relied upon because of the rather extensive length of the connecting lines.

The operation of the FIG. 5 embodiment does differ This first incrementof somewhat during quick-drop from the operation of the embodiment shown in FIGS. 2-4. When quick-drop handle 644 is actuated counterclockwise as seen in FIG. 5, quick-drop cylinder 550 is subjected to air under pressure. However, the pressure chamber of device 532 is also subjected to air under pressure by way of the following circuit: tank 630, line 634, line 654, passage 648, lines 652 and 659, passage 657, line 553, passage 638,

and line 640. Device 532 thereupon pivots stop member 528 out of position for engagement by stop-engaging member 530, and the bowl is free to fall under the influence of gravity.

It may be remarked here that coil 651 of the solenoid which operates valve 691 is always energized and remains energized unless and until switch 612 is operated by the parts taking the position shown in FIG. 3. (Although I 1G. 3 is shown as applying to the embodiment of FIG. 2, the corresponding parts are identical, so that FIG. 3 illustrates the position of these parts for the embodiment of FIG. 5 as well.)

It will be noted from the foregoing description of both embodiments that the additional holding means 23, 3% and 528, 530 is rendered inetiective without the need for any conscious effort to this end by the operator.

It will be evident from the foregoing that this invention provides a safe and reliable device for preventing accidental engagement of element 16 with the supporting surface. This and other objects will be evident from the foregoing to those skilled in the art.

While there are in this application specifically described a plurality of forms which the invention may assume in practice, it will be understood that these forms are shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing rom its spirit or the scope of the appended claims.

What is claimed is:

1. In a vehicle wherein an element can be lowered into contact with the supporting surface: means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface; quick-drop element lowering means associated with said controllable means and including a fluid pressure-operated device and a source of fluid under pressure; additional means for holding the element out of contact with said surface upon failure of said controllable means to so hold the element; and means, responsive to element-lowering action by operatonoperation oi either the controllable means or the quick drop means, actuable to render the additional holding means inetl'ective to hold the element as aforesaid.

2. In a vehicle wherein an element can be lowered into contact with the supporting surface: means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface; quick-drop element lowering means associated with said controllable means and including a fluid pressure-operated device and a source of fluid under pressure; additional means for holding the element out of contact with said surface upon failure of said controllable means to so hold the element and including a stop member, a stop-engaging member, and resilient m ans biasing one of said members into an operating position such that the stop member is engaged by the stop-engaging member upon failure of the controllable means as aforesaid; and fluid pressure-operated means actuable to move said one of the members out of its engaging position and against the bias of the resilient means, and connecting with said source in response to operator-operation of said controllable means or said quick-drop means to lower the element, whereby operator-operation of either said controllable means or said quick-drop means as aforesaid supplies fluid under pressure to said fluid pressure-operated means and moves said one member against the bias of the resilient means.

ill

3. In a vehicle wherein an element can be lowered into contact with the supporting surface: means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface; quick-drop element lowering means associated with said controllable means and including a flui pressure-operated device and a source of fluid under pressure; additional means for holding the element out of contact with said surface upon failure of said controllable means to so hold the element; fluid pressure-operated means ractuable to render the additional holding means ineffective to hold the element as aforesaid; and means to connect said source with the last-named fluid pressureopcrated means in response to operator-operation of said controllable means or said quick-drop means to lower t he element.

4. in a vehicle wherein an element can be lowered into contact with the supporting surface: means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface including a planetary power train having a sun member, a ring member, and a planet member which includes a planet carrier; quiclbdrop element lowering means including a device connected and rotatable with one of the members of said power train, a fluid pressure-operated device to stop rotation of the rotatable device, and a source of fluid under pressure; additional means for bolding the element out of contact with said surface upon failure of said controllable means to so hold the element; a fluid pressure-operated device connected and actuable to render said additional means ineffective; and means connecting the second-named fluid pressure-operated device with said source in response to connection of the firstnamed fluid pressure-operated device with said source or in response to operation of said controllable means for lowering the element.

5. in a vehicle wherein an element can be lowered into contact with the supporting surface: means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface and including a planetary power train having a sun member, a ring member, and a planet member; drive means for said controllable means and connected to drive one of the members of said power train, a second member bein connected to raise and lower said element; quickdrcp element lowering means including a device connected and rotatable with the remaining one of the members of the power train, a fiuid pressure-operated device to stop rotation of the rotatable device and thus constitute the connected member the reaction member of the power train, and a source or" fluid under pressure; additional means for holding the element out or" contact with said surface upon failure of said controllable means to so hold the element; a fluid pressure-operated device connected and actuable to render said additional means ineffective; operator-operable means to connect both fluid pressure-operated devices with said source; and means to connect the second-named fluid pressure opera-ted device with said source in response to operation of said control able means to lower the element.

in a vehicle wherein an element can be lowered into contact with the supporting surface, electric motor means operable to raise and lower the element'and to hold the element out of contact with said surface, a source of electric power, operator-operable means to connect the motor and the power source to raise the element, other operatoroperable means to connect the motor and the power source to lower the element, additional means to lower the element and including a fluid pressure-operated device and a source of fluid under pressure, additional means for holding the element out of contact with said surface upon failure of the motor means to so hold the element, a second fluid pressureoperated device to render the additional holding means ineffective, means operable to connect the second fluid pressure-operated device with the V l l 7 source of fluid under pressure, and electrical means to operate the last-named means in response to operation of either in ans to lower the element.

In a. vehicle wherein element can be lowered into contact with the supporting surface, electric motor means operable to raise and lower the ele em and to hold the element out of contact with said surface, a source of electric power, operator-operable means to connect the motor and the power source to raise or lower the element, additional means to lower the element and including a source of fluid under pressure and a fluid pressureoperated device associated with said motor means, additional means for holding the elements out of contact with said surface upon failure of the motor means to so hold the element, a second fluid pressure-operated device to render the additional holding means ineffective, means operable to connect the second fluid pressure-operated device with the source of fluid under pressure, and electrical means to operate the last-named means in response to operation of either means to lower the element.

8. In a vehicle wherein an element can be lowered into contact with the supporting sur ace, electric motor means operable to raise and lower the element and to hold tile element out of contact with said surface, a source of electric power, operator-operable means to connect the motor and the power source to raise or lower the element, additional means to lower the element and including a source of fluid under pressure and a fluid pressureoperated device associated with said motor means, second operator-operable means to connect the fluid pressure source with the fluid pressure operated device, additional means for holding the element out of contact with said surface upon failure of the motor means to so hold the element, electrically controlled means to render the additional holding means ineffective, and means to operate the electrically controlled means in response to operation of either means to lower the element.

9. In a vehicle wherein an element can be lowered into contact with the supporting surface, electric motor means operable to raise and lower the element and to hold the element out of contact with said surface, a source of electric power, operator-operable means to connect the motor and the power source to raise or lower the element, additional means to lower the element and including a source of fluid under pressure and a fluid pressureoperated device associated with said motor means, second operator-operable means to connect the fluid pressure source with the fluid pressure operated device, additional means for holding the element out of contact with said surface upon failure of the motor means to so hold the element, a second fluid pressure-operated device to render the additional holding means ineflective, means including a valve operable to connect the second fluid pressureoperated device with the source of fluid under pressure, electrical means to operate the valve, a second source of electric power, and means to connect the valve operating means with the second power source and including a first switch operable in response to operation of the first-named operator-operable means to lower the element and a second switch operable in response to operation or" the second operator-operable means.

10. In a vehicle wherein an element can be lowered into contact with the supporting surface, electric motor means operable to raise and lower the element and to hold the element out of contact with said surface, a source of electric power, operator-operable means to connect the motor and the power source to raise or lower the element, additional means to lower the element and including a source of fluid under pressure and a fluid pressureoperatcd device associated with said motor means, second operatoroperable means to connect the fluid pres ure source with the fluid pressure operated device, additional means for holding the element out of contact with said surface upon failure or" the motor means to so hold the element, a second fluidpressure-operated device to render the additional holding means ineflective, means including a valve operable to connect the second fluid pressureoperated device with the source of fluid under pressure, and electrical means, responsive to element lowering action by operator-operation of either operator-operable means, to operate the valve.

11. In a vehicle wherein an element can be lowered into distu r ing engagement with the supporting surface, means controllable by an operator for raising and lowering the element and for holding the element in a position out of contact with said surface, additional means 'for holding the element in said position upon failure of said controllable means to so hold the element, means responsive to element-lowerinc action by operatonoperation of said controllable means actuable to render the additional holding means ineffective to hold the element as aforesaid, and means, operated by the additional holding means, to make the actuable means inoperative during raising and lowering of the element while the element is in disturbing engagement with said surface.

12. A vehicle as in claim 11, in which the actuable means includes an electric circuit having a normally closed switch, and the means to make the actuable means inoperative as aforesaid is arranged to open said switch.

13. A vehicle as in claim 11, in which the actuable means includes an electric circuit having a normally closed switch and a normally open switch, the normally open switch being closed upon operator-operation of the controllable m ans to lower the element, and in which the means to mane the actuable means inoperative as aforesaid is arranged to open the normally closed switch.

References in the file of this patent UNITED STATES PATENTS 

11. IN A VEHICLE WHEREIN AN ELEMENT CAN BE LOWERED INTO DISTURBING ENGAGEMENT WITH THE SUPPORTING SURFACE, MEANS CONTROLLABLE BY AN OPERATOR FOR RAISING AND LOWERING THE ELEMENT AND FOR HOLDING THE ELEMENT IN A POSITION OUT OF CONTACT WITH SAID SURFACE, ADDITIONAL MEANS FOR HOLDING THE ELEMENT IN SAID POSITION UPON FAILURE OF SAID CONTROLLABLE MEANS TO SO HOLD THE ELEMENT, MEANS RESPONSIVE TO ELEMENT-LOWERING ACTION BY OPERATOR-OPERATION OF SAID CONTROLLABLE MEANS ACTUABLE TO RENDER THE ADDITIONAL HOLDING MEANS INEFFECTIVE TO HOLD THE ELEMENT AS AFORESAID, AND MEANS, OPERATED BY THE ADDITIONAL HOLDING MEANS, TO MAKE THE ACTUABLE MEANS INOPERATIVE DURING RAISING AND LOWERING OF THE ELEMENT WHILE THE ELEMENT IS IN DISTURBING ENGAGEMENT WITH SAID SURFACE. 